Process for producing asphalt



Nov. 39, 1940. E. W. GARD ET AL PROCESS FOR PRODUCING ASPHALT Filed July20,- 1937 @a S e R han m 1 7e T, WA A m@ a; Bf .wmhm PQ., mw 5m um 2 QNE 1 FQ: .nl T .5 n@ j, @N @N NN NN w s Nl\ @www Patented Nov. 19, 1940PATENT orifice PROCESS FOR PRODUCING ASPHALT Earle W. Gard, Palos VerdesEstates, and Blair G. Aldridge, Los Angeles, Calif., assignors to UnionOil Company of California, Los Angeles, Calif., a corporation fCalifornia Application `Iuly 20, 1937, Serial No. 154,606

9 Claims.

This invention relates to a process for treating petroleum Oils and inparticular, the invention relates to the production of oxidized or airblown asphalt.

Itis an object of our invention t0 provide a simple, efficient andeconomical process by which petroleum oils may be converted intoasphaltic products of desired penetration, melting point,

` ductility and solubility.

It is a further object of our invention to control the variouscharacteristics of penetration, melting point, ductility and solubilityof asphalt and to vary them independently and at will.

It is a further Object of our invention to control the oxidation of oilto produce asphalt so as to obtain a uniformly oxidized asphalt.

It is an important object of our invention to control the oxidation ofthe oil so as to partially oxidize the oil by contacting it withoxygen-containing gas, to accomplish substantially complete use of theoxygen under controlled conditions, to removethe undesirable gaseous andvaporous products of reaction, to prevent oxidation of vapors in thevapor space of the oxidizing still and to prevent formation ofcarbonaceous and coke-like materials in the still.

It is a further important object of our invention to reduce the timenecessary to air-blow asphalt to the desired grade.

Another important object of our' invention is to reduce the distillationduring oxidation of desirable oil fractions which impart the desiredcharacteristics to the nal product.

It is a further object of our invention to prevent oxidation in thevapor space of the oxidizing still.

Other objects of our invention will appear from the included descriptionof the preferred embodiment of our process appearing below.

The use of air has been employed for many years and is well known in theart of producing oxidized asphalt. However, in the past, it has beenimpossible to produce oxidized asphalts of desired melting point,penetr'ation and ductilities which have a high solubility in CS2, CCl4and 80 gasoline. In these older methods, the penetration, melting pointand ductility are not independently variable. If the melting point isincreased, the penetration is decreased and the ductility is alsodecreased. This is due to the fact 'that the methods used cause some ofthe asphalt to become over-oxidized and part to be under-oxidized andalso there is a considerable amount of distillation during the oxidationperiod. The air passes through the oil in large (Cl. ISG-'74) globulesand is not intimately mixed with all of the cil. In .such methods, therate of oxidation must be fairly slow, otherwise the temperature of theoil will rise too high, with the resultant low yield and poor quality ofasphalt. 5

Also, in the manufacture of oxidized asphalt in the conventional spiderand shell still, it has been found that the oxygen utilization is verypoor and that the spent gases from the still will contain as high as 1'7to 19% of oxygen showing 10' only a 2 to 4% reduction in the oxygencontent of the air. This high oxygen content in the spent gases allowsthe vapors in the vapor space of the still and the vapor lines toundergo oxidation. This oxidation may carry on at such a rate that theVapo-r temperatures will suddenly increase, say from 400 F. to as highas '700 or 800 F. This rapid increase in temperature quite often leadsto vapor explosions with a resulting rupture of the still or explosiondiaphragms built into the l2'() still. Also, when the oxygen content ofthe wasteA gases is high and oxidation takes place in the vapor space,vwe have found upon inspecting the still after completion of a run thatlarge amounts of carbonaceous materials have been formed in the stilland the vapor lines.

We have found, as will appear hereinafter, that by limiting the oxygencontent of the waste gases to around 12%, the tendency to oxidize in y ythe Vapor space is greatly reduced. When the oxygen content of thespentl gases is maintained at around 10%, we find that the oxidation inthe vapor 'space is practically negligible and that the still and vaporlines are kept practically free of any carbonaceous deposits.

In our Patents 1,953,345, 1,953,346 and 1,999,018 we described methodsfor air blowing oils to' produce oxidized asphalts which methods havebeen largely responsible for correcting some of the foregoing evils withthe result that a much better 40 product is produced in considerablyless time. In these methods, the oil to be oxidized is circulated from abulk supply maintained in a cylindrical still or container at anoxidizing temperature to a mixing jet, or other type of mixer known inthe art for commingling a liquid and a gas into which a regulatedquantity of air 0r oxygencontaining gas is admitted. The mixture of oiland air and also vapors are returned to the bulk supply container inwhich the air and vapors are separated from the partially oxidizedcharging stock. The latter is continuously recirculated to the mixeruntil the entire batch ofstock has been oxidized to the predeterminedgrade. By this procedure a superior asphaltic product is `440 gallonsper cubic foot of air.

produced since the oxidation is not as severe, with the result that lesscaribonaceous material is produced and greater ductility and penetrationis obtained at a given flash and melting point. In 5 this method ofoxidation, a better utilization of air is obtained since the oil is moreintimately.

commingled with the air with the attendant result that the oxidation iscompletedin considerably less time than that required by the oldermethods. The present invention relates particularly to improvements inthe foregoing process of oxidation. y

Briefly stated, we have discovered that, in the foregoing method wherecirculation of the oil is employed in order to obtain substantiallycomplete utilization of the oxygen in the air during oxidation, it isnecessary to circulate the oil at a definite ratio per cubic foot of aircontinuously introduced into the mixer. In other words, we havediscovered that the circulation of the oil from the bulk supply to themixer where air is introduced must be controlled so that it exceeds atleast a ratio of gallons per minute per cubic foot of air per minuteinjected into the mixer. We prefer, however, to operate the oxidationreaction with a circulation ratio within a range of 10 to 50 gallons perminute per cubic foot of air per minute with an optimum of -30 gallonsper minute per cubic foot of air per minute. Stated differently, if airis injected into the mixer at a rate of 300 cubic feet per minute, itwill be necessary to circulate the oil from the bulk supply at a ratebetween `3,000 to 15,000 gallons per minute with an optimum circulationof 7,500 to 9,000 gallons per minute. Under such conditions ofoperation, we have found that from to 80% or more of of the oxygen inthe air is consumed by the mixture with an average of about 60 to '70%when the oil is circulated at a ratio of 30 In other words,

with a circulation ratio of approximately 10 gallons of Yoil per minuteto one cubic foot of air per minute, the oxygen content of the spentgases will be in the neighborhood of -about 15% while 4 5 at an oilcirculation ratio of about 45 gallons per cubic foot of air per minute,the oxygen content of the spent gases will fall to as low a figure as 3or 5% and even as low as 1% of oxygen. Heretofore, with lowercirculation ratios of four or five gallons per cubic foot of air, it hasbeen impossible to utilize more than 20% of the oxygen in the air. Ofcourse, the oil-air ratio and the oxygen consumption is a function oftemperature and pressure of oxidation.

Under such increase conditions of oil circula.- tion ratios per cubicfoot of air we have found that for a given maximum oxidation temperatureand a given air rate per barrel of charging stock, increasing thecirculation rate materially 60 decreases the time in which oxidation ofthe charge is completed. The increased efficiency of the air utilizationresults in a marked decrease in the amount of carbonaceous or coke-likematerials in the final product.

Also, the increased circulation rate enables the oxidation to beeffected at a lower temperature. We have found that the lower thetemperature of oxidation, the better will be the air-blowncharacteristics of the final product or in other words, the asphalt willhave a higher melting point for a given penetration and also a higherductility. Stated differently, there are three fundamental occurrencesduringY the oxidation. In the first place, the reaction of the air withthe resinous fractions of the oil results in the production ofadditional bitumens. At the same time, the mutual solvency agents forthe bitumens and cil are destroyed `so that the oil is transferred froma true solution to a colloidal mixture. In the second place, theoxidation of the low viscosity index (V. I.) fractions which flux thebitumens are converted into flux fractions of higher V. I. In the thirdplace, distillation of the ux fractions takes place with the possibilitythat the distillation takes the form of a selective distillation of thehigh V. I. fractions. Generally speaking, the oxidation of the resinsand the oxidation of the low V. I. flux fractions into fractions ofhigher V. I. increase the air blown characteristics of the asphalts. Onthe other hand, the distillation of the flux fractions retard such airblown characteristics. Consequently, by carrying out the oxidationreaction at higher temperatures, the tendency will be to distillconsiderably more of the high V. I. flux fractions. Yet, until recently,it has been impossible to obtain goody oxygen utilization at lowtemperatures due to the fact that the air does not react as readily withthe hydrocarbons at low temperatures. With high circulation ratios,however, we have found that both good oxygen utilization and oxidationat lower temperatures may be obtained. The net results are y that thecharge is oxidized in a much faster time with a lower consumption ofpower and the product will have a higher ductility than asphaltsheretofore produced.

As stated heretofore,r the substantially complete utilization of theoxygen in the oxidation reaction resultsin less coking of the productsthan in cases where the utilization is not as complete. This isprimarily due to the fact that less complete utilization of the oxygenand high temperatures of oxidation results in a combustion of the airand vapors at the surface of the bulk supply of charging stock with theresult that some of the products are converted into coke-like andcarbonaceous materials. In our process, we obtain a more completeutilization of the oxygen in the air and also carry out the oxidationreaction at a substantially lower temperature than temperaturesheretofore employed. We have found it advisable to effect the oxidationreaction at a temperature not above about 475 F. with an optimumtemperature of 450 to 460 F. Yet, we

can accomplish the completion of the oxidation reaction in less timethan heretofore with a higher oxidation temperature but -a lowercirculation ratio.

As a feature of our invention, we have found it to -be desirable tocarry out the oxidation reaction at a lower temperature than thetemperature employed for the greater part of the oxidation reaction. Bymaintaining a temperature of not greater than 400 to 415 F. for thefirst several hours and a temperature of not over 430 F. for the nexthour, we have found that difficulties with the foaming of the contentsin the still are eliminated. Operating in this manner, the still may becharged to as much as 65% of its capacity without trouble due tofoaming. In some instances, it may be desirable to lower the rate 0f airintroduction during the first 11/2 hours of operation in order tominimize foaming of the charge. Thus, on a 200 barrel charge, we mayintroduce air at a rate of about 120 cubic feet per minute for the firsthalf hour which is gradually increased to about 200l cubic feet perminute by the end of the hour and to- 300 cubic feet by the end of thenext half-hour.

The process will be better understood by reference to the drawing whichcontains a more or less schematic embodiment of the apparatus in whichthe process may be carried out. Fig. 1 is a full View of the apparatuswith parts broken away. Fig. 2 is a cross-sectional View taken alongline 2 2 of Fig. 1. Fig. 3 is a cross-sectional View 3 3 of Fig. 2.

In the drawing, Hl is a cylindrical still for containing the bulk supplyof oil to be treated. Still Iii is positioned on a fire-box or furnaceIl. Burners l2 are for supplying heat to the fire-box ll. Line i4,controlled by valve l5, serves to in-' troduce the oil tobe oxidizedinto the still l0. A horizontal baiiie plate I6, extends across thebottom of the still to form a passageway for the oil to the suctionofthe pump to be described. The baiile plate I6 is joined to a verticalplate It at one end adjacent the pump so that all oil entering thepassageway must be drawn into the pump. A small clearance may be leftunder the vertical member to keep a pocket of oil from forming betweenit and the pump end of the still.

A suction |8 extending into the passageway Il. leads to a pump I9 whichis preferably of the vertical type and is provided with a stationary oradjustable screw type pump impeller I9. Pump i9 is provided with shaft20 which is driven electrically by motor 2|. The pump is also providedwith a plurality of straightening vanes 22 which serve to reduce thewhirling motion imparted to the oil by the impeller. Provision is madefor introducing steam and/ or air into the discharge side of the pump.This air may be introduced via line 23 controlled by valve 24 whichpasses through line 25 into a semi-circular spider 2t '.'hich terminatesin each side of the pump casing into two nozzles 21. Likewise, steam maybe introduced into the pump via line 28 controlled by valve 29. Ifdesired, the air or steam may be introduced through these Vanes. Theillustrated arrangement of nozzles in the pump permits an intimateadrnixture of the air and/or steam with the oil passing from the vanes22. Openings 3i) are provided in the pump casing to allow the mixture ofoil, vapors, air and/or steam to pass into the still.

The still i0 is provided with a vapor outlet 3| which is connected to avapor line 32 controlled by valve 33. Condenser 34 serves to cool andcondense vapors. Line 35 serves topass the cooled products into aseparator SS'in which uncondensed gases and vapors may befwithdrawn inline 3l controlled by valve 38. Water `may be withdrawn from the bottomof the separator via f line 39 and oil distillate may be withdrawn fromthe side of the separator via line 48. Provision is mad-e forintroducing chemicals into line 32 in order to prevent the oil fromcondensing as an emulsion. These chemicals may be introduced via line 52provided with valve 53. The water containing the chemicals withdrawnfrom separator 35 via line 39 may be circulated back to line 52. Aschemicals for preventing emulsilcation or for heating emulsions, we mayemploy any of the known materials employed for breaking oil emulsions,such as, for example, sulphonatedA oils, Turkey red oil or any of theknown water softeners.

The still iii is also provided with line 4| controlled by valve 42 whichis employed for pumping out or draining the still I0.

A cooling coil 43 is provided in the still for-cooling the charge duringthe oxidation. Preferably, cooling is obtained by introducing a coolingliquid such as oil taken from tank 44 via lin-e 45 pro` vided with valve4t and pumping it by pump 41 through line 48 and through the coolingvcoils 43. The cooling oil is circulated back to the tank 44 via line 49,cooler 5t and line 5|.

The vapor space of the still is also provided with perforated pipes 51through which oil may be sprayed Via line 55 controlled by valve 56 inorder to scour the sides of the still and the vapor space during theoxidation run and thus greatly reduce the carbonaceous formation. Forthis purpose, part ofthe oil undergoing oxidation in the still,particularly that portion which has passed through the pump casing,maybe circulated by means of a pump into line 55 and. thence through theperforated pipes 5l. It is preferable to spray the oil upwardly so thatthe top and sides of the still are sprayed with the oil. Instead ofusing part of the oil undergoing oxidation for this purpose, a blendingoil may be used provided the proper type of blending oil is selectedwhich when mixed with the oxidized asphalt results in a product havingthe desired characteristics. As blending oils, We may use steam blownasphalt, lubricating oil fractions, gas oil, sulphurized oil, vegetableand animal oils. 'The circulation of the'oil through the perforated pipeis not absolutely essential in cases where the oil-air circulation ratiois suiiiciently high to ensure substantially complete utilization ofoxygen. However, with low circulation ratios and particularly in theconventional spider and shell still operation where air is introduced ata higher rate than can be utilized in the oxidation, we iind thatscouring the sides of the still above the oil level is necessary'toprevent carbonaceous formation on the sides of the still. I

In operation, a hydrocarbon oil, preferably a residuum obtained bydistilling voi tlie'lighter oils, such as kerosene and perhaps gas oilsfrom asphaltic crude oil is introdueedvinto the still lil via lin'e i4and valve l5. When a certain amount of the 'charge is in the still, pumpi3 driven by shaft 20 and motor 2| is started and the oil in the still lis drawn from passageway through openings I8v in the suction side of thepump by impeller I9 which causes the oil to be whirled upwardly past theimpeller. The oil then passes through straightening vanes 22 and backinto the still via openings Si). rihe fire under the still I0 is lightedandthe oil is heated to an oxidation temperature, the temperature beingcontrolled by burner 2. The oil is circulated until the required amountofoil has been introduced into the still through line i4 and until therequired oxidation p Lil, line 43, cooling coil d3, line 4i), cooler'and line'i back to tank i4 in order to maintain the temperature oi thecontents in the still at about 40o-4.1i? F. for the first two hours andat not over. 430 F. for the third hour. The lires in the furnace in themeantime have been turned oil. The balance of the oxidation operationcarried out ata temperature of i-475 F. [is stated previously, it hasbeen :found that still may be charged to capacity and all trouble withfoam avoided if' the still temperature is held bei low 415 F. for therst two hours and 430 F. for the third hour. Similarly, all trouble withloss of vapor temperature control can be avoided if the balance oftheair blowing operation is carried out at temperatures below 475 F. or theoxygen content in the spent gases is kept below about 12%.

In still I0, the vapor and gases are separated from the oil and pass viaoutlet 3| and line 32 to condenser 34 and thence via line 35 intoseparator 36 where oil condensate may be separated from water and gasesand which, if desired, the separated oil may be returned to the stillfor further oxidation. The rate of circulation of the oil through thepump may be controlled by varying vthe speed of the pump through shaftand motor 2 I. The cooling medium such as steam, air or water or oil inthe heat exchanger or cooling coils 43 may be circulated in any desiredamount l 20 in order to obtain the proper degree of cooling by heatexchange out of contact with the oil in the still.

When the charge has been oxidized to the desired degree, the airintroduction via line 28is discontinued. Pump I9 continues to circulatethe charge in the still. Steam is then introduced through the nozzle 2'Iby opening valve 24 and the temperature of the charge is raised to about490500 F. The circulation at about LSD-500 F.

i 30 through the pump and mixing section above the I drawn from still I0via the drain 4I controlled by valve 42.

The following is a specific example for carrying out the presentinvention in order to produce an oxidized asphalt of coating grade: Anasphaltic residuum obtained preferably by distilling from asphaltic baseoil, the light oils and the intermediate boiling oils and specificallyan Orcutt reduced residuum having an A. P. I. gravity of 10.6, a flashof 420 F. (Pensky-Martens closed cup) and a viscosity of 148 secondsSaybolt Furol at 210 F. is preferably preheated and then charged intothe still via line I4 as previously described above. As soon as the oilis in the still, the circulating pump is started and the oil iscirculated at a rate, for example, of 11,000 gallons per minute. Thestill is fired until the oil reaches a temperature of 350 F. When thestill has been charged with 220 bbls. of oil and the charge has reacheda temperature of 350 F., air is introduced into the mixing section ofthe pump via the nozzles 21 at a rate of 120 cubic feet per minute forabout one-half hour. The air rate is then gradually increased until atthe end of the next half hour it will be introduced at a rate of 200cubic feet per minute. B-y the end o f the subsequent half-hour, the airrate will have increased to about 300 cubic feet per minute at whichrate it is maintained until a melting point and penetration is reachedwhich experience has shown it will subsequently produce as` phalt ofapproximately the desired specification. This will require about another10 hours. During the air blowing, the temperature of the charge willhave increased to about 410 F. This temperature is maintained for aboutthe first two hours of the air blowing. It is then increased to about430 F. during the next hour or air blowing at the end of which thetemperature is increased to about 450460 F. where it is maintained forthe balance of the oxidation period. The temperature is maintained andcontrolled by circulating a cooling medium such as oil through thecooling coils in the still to remove the heat of reaction.

When the charge has been brought to near the 5 desired melting point andpenetration, which, as stated heretofore, will require about 11 to 12hoursfrom the beginning of the air blowing, the air rate is reduced toabout 165 cubic feet per minute where it is maintained for the next 2 10hours to bring the asphalt to the desired melting point` and penetrationpreparatory to steam blowing.A It willv be observed at this point thatthe aforementioned reduction of air introduction is made necessarymerely to allow the laboratory 15 to test samples of the charge todetermine the melting point and penetration of the samples and to reportthe same to the vstill operator.v Thus, a better control may be had onthe melting point and penetration characteristics of the 20 charge. Wereit not for this factor, the air rate may be maintained at 300 cubic feetper minute until the completion of the reactionk in which case thereaction m-ay be completed in an additional hour instead of the 2' hoursgiven above 25 which are vrequired subsequent to the reaction in airrate. 'The' above time may be greatly reduced by increasing thetemperature of air rate or both. For some oils, this time will be only 5or 6 hours.

When the charge has been brought to the 30 desired grade preparatory tosteam blowing, the air supply is discontinued and the oxidized charge isheated to approximately 500 F. by re in the still and reducing thecirculation of cooling oil through cooling coils and the oxidized chargeis 35 subjected to steam blowing for about 2 hours. During the steamblowing period, the charge is continuously circulated as during the airblowing period, steam being introduced into the mixing section of thepump by opening valve 24. The '40 aforementioned temperature of 500 F.is maintained during the steam blowing period. The steaming,Y operationpermits light oils to vaporize from the oxidized charge and thus bringthe charge to proper specification. In the example W45 given above, thenal product will have a penetrationof 13 (200 gr. per 60 sec.) at 32 F.,a penetration of 18 (100 gr. per 5 sec.) at 77 F. and a penetration of33 (50 gr. per 5 sec.) at 115 F., a melting point (ball and ring) of 219F., a ilash point (Pensky-Martens closed cup) of 445 F., a ductility of2.2 cm. at 77 F. and solubilities of 99.1% in CS2 ,and CC14 and of 75.7%in 80 gasoline.

The :above description of our invention is not to '450 be considered aslimiting but only as illustrative of the invention and as one mode ofcarrying it out. Many changes can be made within the scope of theinvention which is set forth in the following claims.

We claim:

1. vA process for producing asphalt which comprises commingling oil withoxygen-containing gas at an elevated oxidizing temperature sufficient tooxidize said oil into asphalt, said oxidation being carried out whilecirculating said oil at a high rate from a bulk supply into a mixingdevice into which the oxygen-containing gas is introduced at asubstantially constant rate for the greater part of said oxidation andmaintaining a circulation ratio of 10 to 50 gallons of oil per minuteper cubic foot of air per minute.

2. A process for producing asphalt which comprises circulating oil at anelevated oxidizing temperature, contacting said circulated Oil with freeoxygen-containing gas at a rate of approximately 10-50 gallons perminute per cubic foot of free oxygen-containing gas per minute.

3. A process for producing asphalt which co-mprises circulating oil atan elevated oxidizing temperature, contacting said circulated oil withfree oxygen-containing gas at a rate of approximately 10-50 gallons perminute per cubic foot of free oxygen-containing gas per minute andmaintaining the temperature of said oil at below approximately 475 F.

4. A process forproducing asphalt which comprises maintaining a bulksupply of oil at an elevated oxidizing temperature, circulating said oilfromA said bulk supply through a mixing de- Vice and back to said bulksup-ply and introducing air into said mixing device at a substantiallyconstant rate to oxidize said o-il into asphalt, said circulation of oilthrough said mixing device during said oxidation being at asubstantially constant rate of approximately 10-50 gallons per minuteper cubicfoot of air .per minute introduced into said mixing device.

5. A process for producing asphalt which comprises circulating oil at anelevated oxidizing temperature, commingling said circulated oil withfree oxygen-containing gas at a rate of approximately 10"-50 gallons perminute per cubic foot of free oxygen-containing gas per minute, wherebyapproximately 30 to 80% of the oxygen in said oxygen-containing gas isconsumed by said commingling of oxygen-containing gas with said oil.

6. A process for producing asphalt which com prises circulating oil atan elevated oxidizing temperature, commingling said circulated oil withfree oxygen-containing gas at a rate of approximately -50 gallons perminute per cubic foot of free oxygen-containing gas per minute, wherebyapproximately 30 to 80% of the oxygen in said oxygen-containing gas isconsumed by said commingling of oxygen-containing gas with said oil, andmaintaining the temperature of said oil below approximately 475 F.

7. A process as in claim 2 in which the oil is circulated at a rate ofabout 25-30 gallons per minute per cubic foot of oxygen-containing gas.

8. A process for producing asphalt which cornprises .commingling oilwith free oxygen-containing gas at an elevated oxidizing temperature ina still and during said oxidation spraying the inner surfaces of saidstill above the oil level in said still with oil to prevent oil whichhas splattered on said surfaces during said oxidation from remaining onsaid surfaces for a sufficient period of time to form carbonaceousmaterial.

9. A process as in claim 8 in which said sprayed oil comprises an oilwhich is adapted to be blended with the oil undergoing oxidation.

EARLE W. GARD. BLAIR G. ALDRIDGE..

